If you're rocking a diesel then Terraclean is your friend. I've run one thru annually on Saab and Audi with transformational results - especially handy if you've any DPF issues. I've also done one on my 1.8t BEX petrol, but not with such stunning results. Still good though and something worth doing. Only use a reputable garage though as there are some dodgy mobile agents on the go.
Thanks for that feedback Mark - given you had only recently had an alternative approach done I wasn't sure what to expect with your vehicle, but the difference was incredible - our approach will have cleaned out your turbo.